Question

How many terms of an AP -6,-11/2,-5......, are needed to give the sum of -25

Answer 1

Answer:

5 terms

Step-by-step explanation:

As we know that

Sum of an ap = n/2[2a+(n-1)d]

here sum is = -25

a = -6

d = 0.5

n=?

now

=> -25 = n/2[2(-6)+(n-1)1/2]

=> -25= n/2[-12+(n-1)1/2]

=> n. = 5

Answer 2

Here a=-6

d=1/2

Sum of n terms in ap is=n/2(2a+(n-1)d)=-25

n(-12+(n-1)/2)=50

-12n+n²/2_n/2=50

n²-n-24n=100

n²-25n-100=0

(n-20)(n-5)=0

n=20 or n=5

So no terms needed is 5 or 20